The present invention relates to an internal combustion engine of the type having an auxiliary combustion chamber associated with each main combustion chamber and connected by a torch passage. More particularly, this invention is directed to a manifold system for an internal combustion engine.
Internal combustion engines having an auxiliary combustion chamber associated with each main combustion chamber and connected thereto by a torch passage are well known in the art. A rich air-fuel mixture is supplied to each auxiliary combustion chamber through an auxiliary intake manifold and a lean air-fuel mixture is supplied to each main combustion chamber through a main intake manifold. The total air-fuel (A/F) ratio of the mixtures on which the engines of the above character can operate is great and thus the exhaust gas contain oxygen rich enough for self-oxidation within exhaust manifold of the engine only if it is maintained at elevated temperature.
To vaporize fuel to be supplied to each auxiliary and main combustion chambers of an engine, in a conventional manifold system, heat risers of auxiliary and main intake manifolds are heated with the exhaust gas flowing along an exhaust manifold. This conventional manifold system has a difficulty that when the engine is cold the temperature of the exhaust gas will become too low to facilitate oxidation of noxious components in the exhaust gas because there is a substantial heat transfer from the exhaust manifold to the heat risers.